An orthogonal frequency division multiple access (Orthogonal Frequency Division Multiple Access, OFDMA) technology is a commonly used access technology in the field of modern communications, and a foundation thereof is an orthogonal frequency division multiplexing (Orthogonal Frequency Division Multiplexing, OFDM) technology. In the OFDM technology, a channel is divided into several orthogonal sub-carriers, and a high-speed data signal is converted into parallel low-speed sub data flows, which are modulated onto the sub-carriers for transmission. If the OFDM technology is used, when a plurality of transmitting end devices transmit data to a receiving end device simultaneously, a collision will occur. While in the OFDMA technology, if several consecutive sub-carriers are divided into a sub-channel, different transmitting end devices may be allowed to transmit data to a same receiving end device simultaneously by using different sub-channels, thereby reducing a collision probability between different transmitting end devices. Before transmitting data to the receiving end device on a transmission channel, a transmitting end device first needs to access a channel and transmit a contention request frame to the receiving end device. Subsequently, the receiving end device makes a response, and transmits a scheduling frame including transmission channel allocation information to the transmitting end device.
In an existing mechanism, a transmitting end device transmits a contention request frame to a receiving end device on a selected idle sub-channel. Since the receiving end device acquires channel state information about the transmitting end device on the sub-channel via the contention request frame, that is to say, the receiving end device only can acquire channel state information within a certain consecutive frequency band range, which results in that the receiving end device cannot fully utilize channel resources when performing transmission sub-channel allocation. In this way, a throughput rate of the system will be reduced, and a multi-user selection gain cannot be obtained.